Guide to 3DTV: what is it, how does it work and should you buy one.

Is now the right time to buy a 3D TV?
3D is one of the most interesting technology advances for the home but has had some very mixed reviews and reactions. There are a number of things to consider when you are thinking of buying a new 3DTV or wondering whether it is worth upgrading just for 3D. In the right set-up, 3D can look very impressive, but in other situations you may never even bother to use it.

Background: How does 3D work ?

Digital projectors are at the heart of the 3D cinema revolution – with a special adaptor, a digital projector can easily separate the left and right images.

In contrast, trying to synchronise two traditional mechanical projectors was a tricky process, and often led to blurry images and motion sickness among the audience.

How 3D TV works
We perceive depth because the left eye and right eye are in different locations and each eye captures a subtly different image. The brain processes the two different images into a single image enabling us to perceive the world around us with a sense of depth.

The principle behind 3D TV is exactly the same – two different images are displayed and then shown to the left eye and right eye. Footage of the same image is recorded from two slightly different perspectives, either from two different cameras, or a camera with two lenses.

The footage is interlaced into one image and broadcast. 3D-ready TVs are then able to separate the original 3D broadcast back into separate images. This is done either through polarisation, or rapidly flickering active shutter glasses.
They appear on screen as blurred images – but with the addition of 3D glasses, the separate images are directed to either the right eye or left eye, creating the impression of depth.

3D display formats
There are a number of different techniques employed to produce 3D pictures. The basic principles are the same but the methods of recording, displaying and watching the double images differ.

Anaglyphic 3D
These old style flimsy red/cyan 3D specs are now obsolete and were those worn to view old movies at cinema such as Jaws 3D or House of Wax.

The anaglyphic 3D method was used at cinemas up until very recently, and is the process by which images in a film are constructed of two different coloured layers – usually red and cyan, slightly offset from the original image. With the colour-filtered glasses on, viewers see a different coloured image in each eye.
The red lens allows one eye to see only the red parts of the image and the cyan lens lets the other eye see only the blue/green portions. However, the brain is fooled into perceiving the coloured layers as one, creating an added sense of depth and creating the 3D image.
Compared to the latest techniques the anaglyphic method looks fairly primitive. Poor image quality, blurring and motion sickness were common problems.Polarisation 3D
The polarisation process is the current method used at cinemas to view 3D movies.

The principles are the same as anaglyphic – two slightly different images are seen by each eye, but combined by the brain into one image giving an extra sense of depth – though the delivery method is different.

The glasses work simply by allowing each eye to see differently polarised light. For instance, light polarised in one direction will be seen by the right eye and light polarised in the other by the left.

The technology/glasses are also referred to as ‘passive’ or ‘Cinema 3D, and the glasses worn for TV viewing are very similar to those at cinema. These glasses are light, cheap, and comfortable to wear. However, this technology is only currently adopted for TVs manufactured by one company – LG. The drawback of this technology is that it is currently not suitable for viewing full HD (1080P) images. It is still OK for watching broadcast 3D images from Sky (1080i/720P) and blu ray movies at slightly lower resolution.

Alternate frame sequencing (or frame sequential) 3D(Active shutter glasses)
Footage is recorded by two cameras (or one camera with two lenses) and then placed next to each other on a ‘strip’ of film, and subsequently displayed frame-by-frame, or one after another, in alternating order.

Active shutter glasses are required to view image and work by synchronising with the TV via a wireless signal and rapidly blink on and off, playing back images to the right eye and left eye at a rate of 50 frames per second.

Most new 3D TVs use active shutter technology to display 3D images. The matching glasses typically only work with a specific brand of TV although work is ongoing to make new universal versions.

The glasses are significantly more expensive than the polarised/passive types, and require a battery power source to drive the LCD shutters (either by small watch-type battery, or charged via a USB port). These glasses tend to be heavier and more uncomfortable to wear for long periods.

The advantage of frame sequential method is image quality and capability of displaying full HD 1080P images from 3D Blu Ray movies. The drawbacks are weight/cost of glasses and the fact they can be susceptible to flicker/reflections.

Auto-stereoscopic 3D
The Holy Grail for the 3D TV industry is developing a method of watching in 3D without the viewer having to wear glasses – also known as auto-stereoscopic.

The major electronic companies are investing in this technology and small prototypes have been produced. However it is widely considered that a cost effective, workable system for the mass market is a number of years away

What do I need to watch 3D images on a TV?

In order to view 3D TV, you need a 3D capable TV (or projector), with matching glasses. A 3D source is also required, of which there are 4 types:

HD/3D digibox with subscription to a service provider; Sky or Virgin (which have dedicated 3D TV channel). There is no 3D content available on Freeview or Freesat services.

a 3D Blu-ray player and a 3D version of a Blu-ray movie

a 3D enabled game console and game (eg. Playstation3)

a 3D camcorder – to produce your own 3D family memories.

Note: Many 3D TVs are also capable of artificially converting standard 2D images into 3D, although we have found that this is of limited value.

What should I consider before buying and installing 3D TV ?

Price:
3D TVs (and projectors) are still priced at a small premium above the non-3D versions so if you are on a budget then there are some good bargains at the moment on TV models with same spec but without 3D option. Also consider the cost of glasses – although one pair is usually free, additional pairs can cost upwards from £75 each (this only applies to active shutter glasses).

Technology:
As with all new technology, 3D is evolving, and the newest models should produce the best 3D images. No technology is fully future proof and gradual improvements will be made with each generation of TV. All 3DTVs work with all current 3D sources.

Glasses:
Some of the active shutter glasses used with most of the 3DTVs can become uncomfortable or heavy after wearing for a period of time, so these should be evaluated along with the TV itself. Each TV manufacturer has slightly different glasses design. Most glasses are also battery powered which need replacing or recharging after a period of time.

Image:
3D is all about immersion. It has the ability to improve entertainment by immersing us in the viewing experience. In general, 3DTV provides a much better depth perception into the screen, rather than action leaping out from the screen.

Ghosting and flicker:
Some 3D images can suffer from slight ghosting (double image), caused by the images for each eye overlapping. Older TV models with slower response times (the amount of time it takes a pixel to go from black to white and back again) are more likely to suffer from this problem. Plasma TVs tend to have fastest response time.
Active shutter glasses can also be susceptible to flicker and reflections from background lighting, so compare the effect on some different brands.

Picture brightness:
Wearing a pair of 3D glasses makes the picture appear darker. Therefore, 3D programmes on a TV in a well-lit room, may look rather dim. Many of the newer sets have increased brightness levels for 3D modes. Images for 3D TVs look better in darker environments. Having a dark room also helps eliminate distractions to peripheral vision and enhances the 3D effect.

Screen size:
The size of the display is vital. 3D TV at home is never going to be the fully immersive experience of the cinema. Even on the larger 55-60 inch displays, it is easy to be distracted by glancing at the edge of the screen. In general, the bigger the TV, the better the 3D effect as the image should fill the majority of your peripheral vision. Anything under 42” is not going to be vey useful for 3D viewing. Alternatively, larger size (7-9ft) projector screens are an excellent way to view 3D if you have space!.

Viewing distance/positioning
The smaller the screen, the closer you’ll have to sit to enjoy the full 3D experience. An example guideline for watching a 3D image would ideally be a seating position of 1.8-2M away from a 46-50” screen. This is closer than most people would normally expect. In addition, the 3D effects appear far better from a direct viewing position, so avoid watching on TVs mounted too high or from acute angles. We have also observed that tilting your head sideways can also reduce 3D effect, so you will normally need to sit upright, no slouching or laying down!

How does 3DTV make you feel?
Some people may find the effects of 3D make them feel nauseous. Watching 3D TV clips is more demanding – in a way that normal TV viewing just isn’t, as a certain amount of concentration is required to stay focused on the 3D effect. Usually 1-2 hours of viewing is enough!